WO2022269848A1 - Semiconductor laser - Google Patents

Semiconductor laser Download PDF

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Publication number
WO2022269848A1
WO2022269848A1 PCT/JP2021/023908 JP2021023908W WO2022269848A1 WO 2022269848 A1 WO2022269848 A1 WO 2022269848A1 JP 2021023908 W JP2021023908 W JP 2021023908W WO 2022269848 A1 WO2022269848 A1 WO 2022269848A1
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region
layer
semiconductor laser
diffraction grating
active layer
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PCT/JP2021/023908
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French (fr)
Japanese (ja)
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卓磨 相原
慎治 松尾
優 山岡
達郎 開
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日本電信電話株式会社
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Priority to JP2023529358A priority Critical patent/JPWO2022269848A1/ja
Priority to PCT/JP2021/023908 priority patent/WO2022269848A1/en
Publication of WO2022269848A1 publication Critical patent/WO2022269848A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers

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  • the present invention relates to semiconductor lasers.
  • Non-Patent Document 1 a thin film lateral injection laser capable of wavelength multiplexing and low power consumption is expected.
  • PPR photon-photon resonance
  • the former changes with changes in operating environmental temperature, so in applications where the environmental temperature is extreme, it is necessary to change the injection conditions according to the environmental temperature, which complicates control and prevents stable use of PPR. becomes difficult.
  • the latter similarly has the problem that the control becomes complicated and it is difficult to use the PPR stably, and in addition, the power consumption of the heater is added, so that the power consumption as a whole increases.
  • the prior art has the problem that it is not easy to utilize photon-photon resonance.
  • the present invention has been made to solve the above problems, and aims to facilitate the use of photon-photon resonance.
  • a semiconductor laser comprises: a first clad layer formed on a substrate; an active layer formed on the first clad layer in a core shape extending in a waveguide direction; a p-type semiconductor layer and an n-type semiconductor layer formed in contact with the active layer; a second cladding layer formed on the active layer; and a diffraction grating in a resonator, wherein the resonator includes a first region and a second region having different pitches of the diffraction grating in the waveguide direction, The two regions are spaced apart in the waveguide direction.
  • a semiconductor laser according to the present invention includes a first clad layer formed on a substrate, an active layer formed on the first clad layer in a core shape extending in a waveguide direction, and an active layer comprising: a p-type semiconductor layer and an n-type semiconductor layer formed in contact with the active layer with a second cladding layer formed on the active layer; and a p-type semiconductor layer and a p-electrode connected to the n-type semiconductor layer. and an n-electrode, and an optical coupling layer formed in a core shape extending along the active layer and embedded in the first clad layer or the second clad layer so as to be capable of optically coupling with the active layer, 1.
  • a semiconductor laser having a diffraction grating in a resonator wherein the resonator includes a first region and a second region having different widths of an optical coupling layer in a direction perpendicular to a waveguiding direction. The regions are spaced apart in the waveguide direction.
  • the first region and the second region in which the stop band is modulated are provided in the resonator by changing the pitch of the diffraction grating. , the photon-photon resonance is readily available.
  • FIG. 1A is a cross-sectional view showing the configuration of a semiconductor laser according to Embodiment 1 of the present invention.
  • FIG. 1B is a plan view showing a partial configuration of the semiconductor laser according to Embodiment 1 of the present invention.
  • FIG. 2 is an explanatory diagram for explaining the diffraction grating 110 of the semiconductor laser according to Embodiment 1 of the present invention.
  • FIG. 3 is a band diagram showing how the stop band wavelength in the resonator is modulated by the modulation of the diffraction grating 110.
  • FIG. 4 is a characteristic diagram showing calculation results of the oscillation spectrum of the DFB laser having the stopband shown in FIG. FIG.
  • FIG. 5A is a characteristic diagram showing the calculation result of ⁇ using w2 and gap in FIG. 3 as parameters.
  • FIG. 5B is a characteristic diagram showing the calculation result of the threshold gain difference ⁇ gth using w2 and gap in FIG. 3 as parameters.
  • FIG. 6 is a cross-sectional view showing the configuration of another semiconductor laser according to Embodiment 1 of the present invention.
  • FIG. 7A is a cross-sectional view showing the configuration of a semiconductor laser according to Embodiment 2 of the present invention.
  • 7B is a plan view showing a partial configuration of a semiconductor laser according to Embodiment 2 of the present invention.
  • FIG. FIG. 8A is a cross-sectional view showing the configuration of a semiconductor laser according to Embodiment 3 of the present invention.
  • 8B is a plan view showing a partial configuration of a semiconductor laser according to Embodiment 3 of the present invention.
  • FIG. 8C is a plan view showing a partial configuration of a semiconductor laser according to Em
  • a semiconductor laser according to an embodiment of the present invention will be described below.
  • This semiconductor laser is a DFB (Distributed Feedback) laser comprising an active layer 103 formed in a core shape extending in the waveguide direction on a substrate 101 and having a diffraction grating 110 in the resonator.
  • DFB Distributed Feedback
  • This semiconductor laser first has a first clad layer 102 formed on a substrate 101 and an active layer 103 on the first clad layer 102 .
  • the substrate 101 is made of Si, for example, and the first clad layer 102 is made of silicon oxide, for example. It also has a p-type semiconductor layer 104 and an n-type semiconductor layer 105 formed in contact with the active layer 103 with the active layer 103 interposed therebetween. It also includes a second clad layer 106 formed on the active layer 103 , and a p-electrode 107 and an n-electrode 108 connected to the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
  • the p-type semiconductor layer 104 and the n-type semiconductor layer 105 are formed by introducing impurities into the semiconductor layer 109 made of InP, for example.
  • the active layer 103 is embedded in the semiconductor layer 109 between the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
  • diffraction grating 110 can be formed at the interface between semiconductor layer 109 and second cladding layer 106 .
  • the semiconductor laser according to Embodiment 1 includes a first region 121 and a second region 122 whose stopbands are modulated in the resonator, as shown in FIG. 1B.
  • the first region 121 and the second region 122 are spaced apart in the waveguide direction.
  • the first region 121 and the second region 122 modulate the stop band by changing the pitch of the diffraction grating 110 .
  • the first region 121 and the second region 122 have a different pitch of the diffraction grating 110 in the waveguide direction than the other regions.
  • the pitch of the diffraction grating 110 in the first region 121 is made larger than that in other regions, and the pitch of the diffraction grating 110 in the second region 122 is made smaller than those in other regions.
  • the pitch of the diffraction gratings 110 in the first region 121 can be twice the pitch of the diffraction gratings 110 in the second region 122 .
  • FIG. 1B is a plan view showing the configuration of the diffraction grating 110, and the waveguiding direction is the direction from the right to the left on the page of FIG. 1B.
  • a third region 123 and a fourth region 124 whose stopbands are modulated are provided at both ends of the resonator.
  • the third region 123 and fourth region 124 modulate the stop band by changing the duty ratio of the diffraction grating 110 .
  • the duty ratio of the diffraction grating 110 in the waveguide direction of the third region 123 on one end side and the fourth region 124 on the other end side in the resonator is higher than the duty ratio of the region inside the third region 123 and the fourth region 124. made smaller.
  • the pitch and duty ratio of the diffraction grating 110 are modulated as shown in FIG.
  • the stop band wavelength in the resonator is modulated as shown in FIG.
  • the stop band wavelength of the first region 121 with the increased pitch of the diffraction grating 110 shifts to the longer wavelength side.
  • the third region 123 and the fourth region 124 in which the duty ratio of the diffraction grating 110 is reduced have a narrow stop band width.
  • Figure 4 shows the calculation result of the oscillation spectrum of a DFB laser having a stop band as shown in Figure 3.
  • a dominant mode and a minor mode appear at adjacent wavelengths.
  • ⁇ be the wavelength difference between the main mode and the sub mode.
  • DFB lasers basically oscillate at the wavelength of the dominant mode.
  • PPR photon-photon resonance
  • threshold gain difference between the primary mode and the secondary mode to prevent multimode oscillation.
  • PPR can be expressed without requiring an external resonator in addition to the DFB laser. Therefore, it is not necessary to match the phases of the light emitted from the DFB laser and the feedback light.
  • a phase adjustment mechanism for example, a heater
  • modulation regions of the first region 121 and the second region 122 and the third region 123 and the fourth region 124 of the diffraction grating 110 are modulated with smooth functions. This is because a sudden change in pitch or duty ratio increases the scattering loss.
  • Modulation functions include parabolic functions, Gaussian functions, Lorentzian functions, and the like.
  • an optical coupling layer 111 formed in a core shape extending along the active layer 103 and embedded in the first clad layer 102 in a state capable of optically coupling with the active layer 103 is further added.
  • the optical coupling layer 111 can be made of single crystal silicon, for example.
  • This semiconductor laser is a DFB laser having an active layer 103 formed in a core shape extending in the waveguide direction on a substrate 101 and having a diffraction grating 112 in the resonator.
  • This semiconductor laser first has a first clad layer 102 formed on a substrate 101 and an active layer 103 on the first clad layer 102 .
  • the substrate 101 is made of Si, for example, and the first clad layer 102 is made of silicon oxide, for example. It also has a p-type semiconductor layer 104 and an n-type semiconductor layer 105 formed in contact with the active layer 103 with the active layer 103 interposed therebetween. It also includes a second clad layer 106 formed on the active layer 103 , and a p-electrode 107 and an n-electrode 108 connected to the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
  • the p-type semiconductor layer 104 and the n-type semiconductor layer 105 are formed by introducing impurities into the semiconductor layer 109 made of InP, for example.
  • the active layer 103 is embedded in the semiconductor layer 109 between the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
  • an optical coupling layer 113 formed in a core shape extending along the active layer 103 is embedded in the first clad layer 102 so as to be optically coupled with the active layer 103 .
  • the optical coupling layer 113 can be made of single crystal silicon, for example.
  • the semiconductor laser according to the embodiment includes a first region 121 and a second region 122 whose stopbands are modulated in the resonator, as shown in FIG. 7B.
  • the first region 121 and the second region 122 are spaced apart in the waveguide direction.
  • the first region 121 and the second region 122 modulate the stopband by changing the width of the optical coupling layer 113 .
  • the first region 121 and the second region 122 are different from other regions in the width of the optical coupling layer 113 in the waveguide direction. Also, the width of the optical coupling layer 113 in the first region 121 is made larger than that in other regions, and the width of the optical coupling layer 113 in the second region 122 is made smaller than that in other regions. Note that FIG. 7B is a plan view showing the configuration of the optical coupling layer 113, and the direction from the right to the left on the paper surface of FIG. 7B is the waveguide direction.
  • a third region 123 and a fourth region 124 whose stopbands are modulated are provided at both ends of the resonator.
  • the third region 123 and fourth region 124 also modulate the stopband by changing the width of the optical coupling layer 113 .
  • the width of the optical coupling layer 113 in the waveguide direction of the third region 123 on one end side and the fourth region 124 on the other end side in the resonator is larger than the width of the region inside the third region 123 and the fourth region 124 . It is
  • the optical coupling layer 113 As described above, by providing the optical coupling layer 113 and changing the width of the optical coupling layer 113 in the first region 121, the second region 122, the third region 123, and the fourth region 124, the optical coupling layer 113 shown in FIG. As shown, the stopband wavelength in the cavity is modulated.
  • the width of the optical coupling layer 113 By changing the width of the optical coupling layer 113, the coupling coefficient of the diffraction grating 112 and the rate of optical confinement in the active layer 103 can be changed, and as described above, the stopband wavelength in the resonator can be modulated. can.
  • the stop band wavelength in the resonator can be modulated. can be expressed. Therefore, it is not necessary to match the phases of the light emitted from the DFB laser and the feedback light. As a result, in the second embodiment as well, the PPR is generated even if the current injection conditions are not specific for the DFB laser, so high-speed direct modulation is realized regardless of the operating environment. Moreover, since the second embodiment does not require a phase adjustment mechanism such as a heater, it is effective in reducing power consumption.
  • This semiconductor laser is a DFB laser having an active layer 103 formed in a core shape extending in the waveguide direction on a substrate 101 and having a diffraction grating 114 in the resonator.
  • This semiconductor laser first has a first clad layer 102 formed on a substrate 101 and an active layer 103 on the first clad layer 102 .
  • the substrate 101 is made of Si, for example, and the first clad layer 102 is made of silicon oxide, for example. It also has a p-type semiconductor layer 104 and an n-type semiconductor layer 105 formed in contact with the active layer 103 with the active layer 103 interposed therebetween. It also includes a second clad layer 106 formed on the active layer 103 , and a p-electrode 107 and an n-electrode 108 connected to the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
  • the p-type semiconductor layer 104 and the n-type semiconductor layer 105 are formed by introducing impurities into the semiconductor layer 109 made of InP, for example.
  • the active layer 103 is embedded in the semiconductor layer 109 between the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
  • an optical coupling layer 113 formed in a core shape extending along the active layer 103 is embedded in the first clad layer 102 so as to be optically coupled with the active layer 103 .
  • the optical coupling layer 113 can be made of single crystal silicon, for example.
  • the semiconductor laser according to the embodiment includes, as shown in FIG. 8B, a first region 121 and a second region 122 whose stopbands are modulated in the resonator.
  • the first region 121 and the second region 122 are spaced apart in the waveguide direction.
  • the first region 121 and the second region 122 modulate the stopband by changing the width of the optical coupling layer 113 .
  • the first region 121 and the second region 122 are different from other regions in the width of the optical coupling layer 113 in the waveguide direction. Also, the width of the optical coupling layer 113 in the first region 121 is made larger than that in other regions, and the width of the optical coupling layer 113 in the second region 122 is made smaller than that in other regions. Note that FIG. 8B is a plan view showing the configuration of the optical coupling layer 113, and the direction from the right to the left on the paper surface of FIG. 8B is the waveguide direction.
  • the third region 123 and the fourth region 124 whose stopbands are modulated are provided at both ends in the resonator.
  • the third region 123 and fourth region 124 modulate the stop band by changing the duty ratio of the diffraction grating 114 .
  • the duty ratio of the diffraction grating 114 in the waveguide direction of the third region 123 on one end side and the fourth region 124 on the other end side in the resonator is higher than the duty ratio of the region inside the third region 123 and the fourth region 124. made smaller.
  • the stop band wavelengths of the 3rd region 123 and the 4th region 124 are modulated.
  • the stop band wavelength in the resonator can be modulated. can be expressed. Therefore, it is not necessary to match the phases of the light emitted from the DFB laser and the feedback light.
  • the PPR is generated without the specific current injection conditions of the DFB laser, so high-speed direct modulation is realized regardless of the operating environment.
  • the third embodiment does not require a phase adjustment mechanism such as a heater, it is effective in reducing power consumption.
  • the first region and the second region in which the stop band is modulated are provided in the resonator by changing the pitch of the diffraction grating. etc., making photon-photon resonance readily available.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)

Abstract

This semiconductor layer is a DFB laser comprising: on a substrate (101), an active layer (103) that extends in a waveguide direction and that is formed in a core shape; a diffraction grating (110) in the resonator; and, in the resonator, a first area (121) and a second area (122) the stop bands of which have been modulated. The first area (121) and the second area (122) are separated by a distance in the waveguide direction. The stop bands of the first area (121) and the second area (122) have been modulated by changing the pitch of the diffraction grating (110).

Description

半導体レーザsemiconductor laser
　本発明は、半導体レーザに関する。 The present invention relates to semiconductor lasers.
　インターネットなどにおける通信トラフィックの増加に伴い、情報伝送の高速・大容量化が求められている。特にデータセンタ内においては、小型・低コスト、低消費電力、高速変調可能な直接変調レーザが求められる。 With the increase in communication traffic on the Internet, etc., there is a demand for high-speed and large-capacity information transmission. Especially in data centers, direct modulation lasers that are compact, low cost, low power consumption, and capable of high-speed modulation are required.
　今後の大容量化に向けては、さらなるレーザの高速化および複数のレーザを用いた波長多重化、同時に低消費電力化が望まれる。この要求に対し、波長多重が可能かつ低消費電力な薄膜横方向注入型レーザが期待されている（非特許文献１）。 In order to increase the capacity in the future, it is desirable to further increase the laser speed, wavelength multiplex using multiple lasers, and reduce power consumption at the same time. In response to this demand, a thin film lateral injection laser capable of wavelength multiplexing and low power consumption is expected (Non-Patent Document 1).
　このレーザの高速化に向けて、光子－光子共鳴（ＰＰＲ：photon-photon resonance）の利用が有用である。ＰＰＲとは、レーザに光のフィードバック機構を設けてなされる変調帯域拡大の技術であり、次の理由により変調帯域が拡大する。 The use of photon-photon resonance (PPR) is useful for increasing the speed of this laser. PPR is a technique for expanding the modulation band by providing a laser with an optical feedback mechanism, and the modulation band is expanded for the following reasons.
　例えば、分布帰還型（ＤＦＢ）レーザにファブリペロー共振器を加えた構造を考える。レーザからの出射光は、ファブリペロー共振器から反射されレーザに光がフィードバックされる。このフィードバック光の位相が出射光の位相と同相の場合、レーザ内での光パワーは強め合い、共鳴的に光パワーは増強する。レーザの変調周波数がファブリペロー共振器の共振周波数と一致していれば、その変調周波数で変調度が高くなる。したがって、共振周波数と位相を適切に調整することで直接変調レーザの変調帯域を拡大することが可能となる。実際に、非特許文献２に示すように、ＰＰＲを利用することにより、高速な直接変調を実現している。 For example, consider a structure in which a Fabry-Perot resonator is added to a distributed feedback (DFB) laser. Light emitted from the laser is reflected from the Fabry-Perot resonator and fed back to the laser. When the phase of this feedback light is the same as the phase of the output light, the optical powers in the laser reinforce each other, and the optical power increases in resonance. If the modulation frequency of the laser matches the resonance frequency of the Fabry-Perot resonator, the degree of modulation increases at that modulation frequency. Therefore, it is possible to expand the modulation band of the directly modulated laser by appropriately adjusting the resonance frequency and phase. In fact, as shown in Non-Patent Document 2, high-speed direct modulation is realized by using PPR.
　しかしながら、上述した技術では、レーザからの出射光とフィードバック光の位相を同相にする必要があり、このためには、レーザの特定の電流注入条件、あるいはファブリペロー共振器の位相調整機構（例えばヒータ）が必要となる。 However, in the above-described technique, it is necessary to make the phases of the emitted light from the laser and the feedback light in phase. )Is required.
　前者は、動作環境温度の変化に対して変化するため、環境温度の激しい用途においては、環境温度に合わせて注入条件を変える必要があり、制御が複雑になるうえ安定的にＰＰＲを利用することが難しくなる。後者も同様に、制御が複雑になるうえ安定的にＰＰＲを利用することが難しく、加えてヒータでの消費電力が付加されるため全体としての消費電力は大きくなる問題がある。このように、従来技術では、光子－光子共鳴を利用することが容易ではないという問題があった。 The former changes with changes in operating environmental temperature, so in applications where the environmental temperature is extreme, it is necessary to change the injection conditions according to the environmental temperature, which complicates control and prevents stable use of PPR. becomes difficult. The latter similarly has the problem that the control becomes complicated and it is difficult to use the PPR stably, and in addition, the power consumption of the heater is added, so that the power consumption as a whole increases. Thus, the prior art has the problem that it is not easy to utilize photon-photon resonance.
　本発明は、以上のような問題点を解消するためになされたものであり、光子－光子共鳴が容易に利用できるようにすることを目的とする。 The present invention has been made to solve the above problems, and aims to facilitate the use of photon-photon resonance.
　本発明に係る半導体レーザは、基板の上に形成された第１クラッド層と、第１クラッド層の上に、導波方向に延在するコア形状に形成された活性層と、活性層を挾んで活性層に接して形成されたｐ型半導体層およびｎ型半導体層と、活性層の上に形成された第２クラッド層と、ｐ型半導体層およびｎ型半導体層に接続するｐ電極およびｎ電極とを備え、共振器内に回折格子を備える半導体レーザであって、共振器内に、導波方向の回折格子のピッチが各々異なる第１領域および第２領域を備え、第１領域と第２領域とは、導波方向に間隔を開けて配置されている。 A semiconductor laser according to the present invention comprises: a first clad layer formed on a substrate; an active layer formed on the first clad layer in a core shape extending in a waveguide direction; a p-type semiconductor layer and an n-type semiconductor layer formed in contact with the active layer; a second cladding layer formed on the active layer; and a diffraction grating in a resonator, wherein the resonator includes a first region and a second region having different pitches of the diffraction grating in the waveguide direction, The two regions are spaced apart in the waveguide direction.
　また、本発明に係る半導体レーザは、基板の上に形成された第１クラッド層と、第１クラッド層の上に、導波方向に延在するコア形状に形成された活性層と、活性層を挾んで活性層に接して形成されたｐ型半導体層およびｎ型半導体層と、活性層の上に形成された第２クラッド層と、ｐ型半導体層およびｎ型半導体層に接続するｐ電極およびｎ電極と、活性層と光結合可能な状態で第１クラッド層または第２クラッド層に埋め込まれて、活性層に沿って延在するコア形状に形成された光結合層とを備え、共振器内に回折格子を備える半導体レーザであって、共振器内に、導波方向に垂直な方向の光結合層の幅が各々異なる第１領域および第２領域を備え、第１領域と第２領域とは、導波方向に間隔を開けて配置されている。 A semiconductor laser according to the present invention includes a first clad layer formed on a substrate, an active layer formed on the first clad layer in a core shape extending in a waveguide direction, and an active layer comprising: a p-type semiconductor layer and an n-type semiconductor layer formed in contact with the active layer with a second cladding layer formed on the active layer; and a p-type semiconductor layer and a p-electrode connected to the n-type semiconductor layer. and an n-electrode, and an optical coupling layer formed in a core shape extending along the active layer and embedded in the first clad layer or the second clad layer so as to be capable of optically coupling with the active layer, 1. A semiconductor laser having a diffraction grating in a resonator, wherein the resonator includes a first region and a second region having different widths of an optical coupling layer in a direction perpendicular to a waveguiding direction. The regions are spaced apart in the waveguide direction.
　以上説明したように、本発明によれば、回折格子のピッチを変えるなどにより、共振器内にストップバンドが変調された第１領域および第２領域を備えるようにしたので、分布帰還型レーザなどにおいて、光子－光子共鳴が容易に利用できる。 As described above, according to the present invention, the first region and the second region in which the stop band is modulated are provided in the resonator by changing the pitch of the diffraction grating. , the photon-photon resonance is readily available.
図１Ａは、本発明の実施の形態１に係る半導体レーザの構成を示す断面図である。FIG. 1A is a cross-sectional view showing the configuration of a semiconductor laser according to Embodiment 1 of the present invention. 図１Ｂは、本発明の実施の形態１に係る半導体レーザの一部構成を示す平面図である。FIG. 1B is a plan view showing a partial configuration of the semiconductor laser according to Embodiment 1 of the present invention. 図２は、本発明の実施の形態１に係る半導体レーザの回折格子１１０を説明するための説明図である。FIG. 2 is an explanatory diagram for explaining the diffraction grating 110 of the semiconductor laser according to Embodiment 1 of the present invention. 図３は、回折格子１１０の変調により、共振器におけるストップバンド波長が変調される状態を示すバンド図である。FIG. 3 is a band diagram showing how the stop band wavelength in the resonator is modulated by the modulation of the diffraction grating 110. In FIG. 図４は、図３に示すストップバンドを有するＤＦＢレーザの発振スペクトルの計算結果を示す特性図である。FIG. 4 is a characteristic diagram showing calculation results of the oscillation spectrum of the DFB laser having the stopband shown in FIG. 図５Ａは、図３のｗ２およびｇａｐをパラメータとしたΔλの計算結果を示す特性図である。FIG. 5A is a characteristic diagram showing the calculation result of Δλ using w2 and gap in FIG. 3 as parameters. 図５Ｂは、図３のｗ２およびｇａｐをパラメータとした閾値利得差Δｇｔｈの計算結果を示す特性図である。FIG. 5B is a characteristic diagram showing the calculation result of the threshold gain difference Δgth using w2 and gap in FIG. 3 as parameters. 図６は、本発明の実施の形態１に係る他の半導体レーザの構成を示す断面図である。FIG. 6 is a cross-sectional view showing the configuration of another semiconductor laser according to Embodiment 1 of the present invention. 図７Ａは、本発明の実施の形態２に係る半導体レーザの構成を示す断面図である。FIG. 7A is a cross-sectional view showing the configuration of a semiconductor laser according to Embodiment 2 of the present invention. 図７Ｂは、本発明の実施の形態２に係る半導体レーザの一部構成を示す平面図である。7B is a plan view showing a partial configuration of a semiconductor laser according to Embodiment 2 of the present invention. FIG. 図８Ａは、本発明の実施の形態３に係る半導体レーザの構成を示す断面図である。FIG. 8A is a cross-sectional view showing the configuration of a semiconductor laser according to Embodiment 3 of the present invention. 図８Ｂは、本発明の実施の形態３に係る半導体レーザの一部構成を示す平面図である。8B is a plan view showing a partial configuration of a semiconductor laser according to Embodiment 3 of the present invention. FIG. 図８Ｃは、本発明の実施の形態３に係る半導体レーザの一部構成を示す平面図である。8C is a plan view showing a partial configuration of a semiconductor laser according to Embodiment 3 of the present invention. FIG.
　以下、本発明の実施の形態に係る半導体レーザについて説明する。 A semiconductor laser according to an embodiment of the present invention will be described below.
［実施の形態１］
　はじめに、本発明の実施の形態１に係る半導体レーザについて図１Ａ、図１Ｂを参照して説明する。この半導体レーザは、基板１０１の上に、導波方向に延在するコア形状に形成された活性層１０３を備え、共振器内に回折格子１１０を備えるＤＦＢ（Distributed Feedback）レーザである。 [Embodiment 1]
First, a semiconductor laser according to Embodiment 1 of the present invention will be described with reference to FIGS. 1A and 1B. This semiconductor laser is a DFB (Distributed Feedback) laser comprising an active layer 103 formed in a core shape extending in the waveguide direction on a substrate 101 and having a diffraction grating 110 in the resonator.
　この半導体レーザは、まず、基板１０１の上に第１クラッド層１０２が形成され、第１クラッド層１０２の上に、活性層１０３を備える。基板１０１は、例えば、Ｓｉから構成され、第１クラッド層１０２は、例えば、酸化シリコンから構成されている。また、活性層１０３を挾んで活性層１０３に接して形成されたｐ型半導体層１０４およびｎ型半導体層１０５を備える。また、活性層１０３の上に形成された第２クラッド層１０６と、ｐ型半導体層１０４およびｎ型半導体層１０５に接続するｐ電極１０７およびｎ電極１０８とを備える。 This semiconductor laser first has a first clad layer 102 formed on a substrate 101 and an active layer 103 on the first clad layer 102 . The substrate 101 is made of Si, for example, and the first clad layer 102 is made of silicon oxide, for example. It also has a p-type semiconductor layer 104 and an n-type semiconductor layer 105 formed in contact with the active layer 103 with the active layer 103 interposed therebetween. It also includes a second clad layer 106 formed on the active layer 103 , and a p-electrode 107 and an n-electrode 108 connected to the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
　この例では、ｐ型半導体層１０４およびｎ型半導体層１０５は、例えば、ＩｎＰからなる半導体層１０９に不純物を導入することで形成されている。また、ｐ型半導体層１０４とｎ型半導体層１０５との間において、活性層１０３は、半導体層１０９に埋め込まれて形成されている。例えば、回折格子１１０は、半導体層１０９と第２クラッド層１０６との界面に形成することができる。 In this example, the p-type semiconductor layer 104 and the n-type semiconductor layer 105 are formed by introducing impurities into the semiconductor layer 109 made of InP, for example. Also, the active layer 103 is embedded in the semiconductor layer 109 between the p-type semiconductor layer 104 and the n-type semiconductor layer 105 . For example, diffraction grating 110 can be formed at the interface between semiconductor layer 109 and second cladding layer 106 .
　上述した構成に加え、実施の形態１に係る半導体レーザは、図１Ｂに示すように、共振器内に、ストップバンドが変調された第１領域１２１および第２領域１２２を備える。第１領域１２１と第２領域１２２とは、導波方向に間隔を開けて配置されている。第１領域１２１および第２領域１２２は、回折格子１１０のピッチを変えることで、ストップバンドを変調させている。 In addition to the configuration described above, the semiconductor laser according to Embodiment 1 includes a first region 121 and a second region 122 whose stopbands are modulated in the resonator, as shown in FIG. 1B. The first region 121 and the second region 122 are spaced apart in the waveguide direction. The first region 121 and the second region 122 modulate the stop band by changing the pitch of the diffraction grating 110 .
　第１領域１２１および第２領域１２２は、導波方向の回折格子１１０のピッチが他の領域とは異なるものとされている。また、第１領域１２１の回折格子１１０のピッチは、他の領域より大きくされ、第２領域１２２の回折格子１１０のピッチは、他の領域より小さくされている。例えば、第１領域１２１の回折格子１１０のピッチは、第２領域１２２の回折格子１１０のピッチの２倍とすることができる。なお、図１Ｂは、回折格子１１０の構成を示す平面図であり、図１Ｂの紙面右から左の方向が、導波方向となっている。 The first region 121 and the second region 122 have a different pitch of the diffraction grating 110 in the waveguide direction than the other regions. Also, the pitch of the diffraction grating 110 in the first region 121 is made larger than that in other regions, and the pitch of the diffraction grating 110 in the second region 122 is made smaller than those in other regions. For example, the pitch of the diffraction gratings 110 in the first region 121 can be twice the pitch of the diffraction gratings 110 in the second region 122 . Note that FIG. 1B is a plan view showing the configuration of the diffraction grating 110, and the waveguiding direction is the direction from the right to the left on the page of FIG. 1B.
　また、この例では、共振器内の両端に、ストップバンドが変調された第３領域１２３および第４領域１２４を備える。第３領域１２３および第４領域１２４は、回折格子１１０のデューティー比を変えることで、ストップバンドを変調させている。共振器内の一端側の第３領域１２３および他端側の第４領域１２４の導波方向の回折格子１１０のデューティー比は、第３領域１２３および第４領域１２４より内側の領域のデューティー比より小さくされている。 Also, in this example, a third region 123 and a fourth region 124 whose stopbands are modulated are provided at both ends of the resonator. The third region 123 and fourth region 124 modulate the stop band by changing the duty ratio of the diffraction grating 110 . The duty ratio of the diffraction grating 110 in the waveguide direction of the third region 123 on one end side and the fourth region 124 on the other end side in the resonator is higher than the duty ratio of the region inside the third region 123 and the fourth region 124. made smaller.
　回折格子１１０のピッチ（pitch）およびデューティー（ｄｕｔｙ）比は、図２に示すように変調している。この回折格子１１０の変調により、共振器におけるストップバンド波長は、図３に示す形に変調される。例えば、回折格子１１０のピッチを大きくした第１領域１２１のストップバンド波長は、長波側にシフトする。また、回折格子１１０のｄｕｔｙ比を小さくした第３領域１２３、第４領域１２４は、ストップバンド幅が狭くなる。 The pitch and duty ratio of the diffraction grating 110 are modulated as shown in FIG. By modulating the diffraction grating 110, the stop band wavelength in the resonator is modulated as shown in FIG. For example, the stop band wavelength of the first region 121 with the increased pitch of the diffraction grating 110 shifts to the longer wavelength side. In addition, the third region 123 and the fourth region 124 in which the duty ratio of the diffraction grating 110 is reduced have a narrow stop band width.
　図３に示すようなストップバンドを有するＤＦＢレーザの発振スペクトルの計算結果を図４に示す。図４に示すように、主モードおよびそれと隣接した波長で副モードが現れる。ここで、主モードと副モードとの波長差をΔλとする。基本的にＤＦＢレーザは、主モードの波長で発振する。このレーザを直接変調した際、レーザの変調周波数がΔλと一致していれば、主モードと副モードが共振器内で強め合い、共鳴的に光パワーが増強するため、Δλと一致する変調周波数で変調度が高くなる。 　Figure 4 shows the calculation result of the oscillation spectrum of a DFB laser having a stop band as shown in Figure 3. As shown in FIG. 4, a dominant mode and a minor mode appear at adjacent wavelengths. Here, let Δλ be the wavelength difference between the main mode and the sub mode. DFB lasers basically oscillate at the wavelength of the dominant mode. When this laser is directly modulated, if the modulation frequency of the laser matches Δλ, the main mode and the sub mode strengthen each other in the resonator, and the optical power is resonantly enhanced, so the modulation frequency matches Δλ , the degree of modulation increases.
　Δλの値は、図３のｗ２およびｇａｐにより調整することができる。ｗ２およびｇａｐをパラメータとしたΔλの計算結果を図５Ａに示す。図５Ａに示すように、ｗ２を－２０ｎｍ程度（ｗ１の符号が反転しかつ２倍程度）にすると、Δλが減少することが分かる。また、ｇａｐを大きくするとΔλが減少することが分かる。特にｗ２＝－２０ｎｍ、ｇａｐ＝３０μｍとすると、Δλ＝０．８ｎｍ（Δｆ＝１００ＧＨｚ）程度になることが分かる。これは変調帯域特性として、変調周波数１００ＧＨｚ付近において、光子－光子共鳴（ＰＰＲ）により変調度が向上することを意味する。 The value of Δλ can be adjusted by w2 and gap in FIG. Calculation results of Δλ with w2 and gap as parameters are shown in FIG. 5A. As shown in FIG. 5A, it can be seen that Δλ decreases when w2 is set to approximately −20 nm (the sign of w1 is inverted and approximately doubled). Also, it can be seen that Δλ decreases when the gap is increased. In particular, when w2=−20 nm and gap=30 μm, Δλ=0.8 nm (Δf=100 GHz). As a modulation band characteristic, this means that the degree of modulation is improved by photon-photon resonance (PPR) near the modulation frequency of 100 GHz.
　また、マルチモード発振させないために主モードと副モードとの間で閾値利得差を与える必要がある。図５Ｂに示すように、ｗ２＝－２０ｎｍ付近では、３０ｃｍ-1程度の閾値利得差Δｇｔｈがあり、単一モード発振させるには十分な値である。 Also, it is necessary to provide a threshold gain difference between the primary mode and the secondary mode to prevent multimode oscillation. As shown in FIG. 5B, there is a threshold gain difference Δgth of about 30 cm −1 near w2=−20 nm, which is a sufficient value for single-mode oscillation.
　以上の構造では、ＤＦＢレーザとは別に外部共振器を必要とせずともＰＰＲを発現することができる。このため、ＤＦＢレーザからの出射光とフィードバック光の位相を合わせる必要がなくなる。この結果、実施の形態１によれば、ＤＦＢレーザの特定の電流注入条件でなくともＰＰＲが発現するため、動作環境によらず高速な直接変調が実現する。また、実施の形態１によれば、位相調整機構（例えばヒータなど）を必要としないため、低消費電力化に対して有効である。 With the above structure, PPR can be expressed without requiring an external resonator in addition to the DFB laser. Therefore, it is not necessary to match the phases of the light emitted from the DFB laser and the feedback light. As a result, according to Embodiment 1, since PPR is generated even if the current injection condition of the DFB laser is not specific, high-speed direct modulation is realized regardless of the operating environment. Moreover, according to Embodiment 1, since a phase adjustment mechanism (for example, a heater) is not required, it is effective in reducing power consumption.
　なお、回折格子１１０の第１領域１２１および第２領域１２２や、第３領域１２３および第４領域１２４の変調領域は、滑らかな関数で変調させる。これは、急激なピッチやｄｕｔｙ比の変化は、散乱損失を増加させるためである。変調の関数としては、放物線関数、ガウス関数、ローレンツ関数など挙げられる。 The modulation regions of the first region 121 and the second region 122 and the third region 123 and the fourth region 124 of the diffraction grating 110 are modulated with smooth functions. This is because a sudden change in pitch or duty ratio increases the scattering loss. Modulation functions include parabolic functions, Gaussian functions, Lorentzian functions, and the like.
　なお、図６に示すように、活性層１０３と光結合可能な状態で第１クラッド層１０２に埋め込まれて、活性層１０３に沿って延在するコア形状に形成された光結合層１１１をさらに備えることができる。光結合層１１１は、例えば、単結晶シリコンから構成することができる。 As shown in FIG. 6, an optical coupling layer 111 formed in a core shape extending along the active layer 103 and embedded in the first clad layer 102 in a state capable of optically coupling with the active layer 103 is further added. be prepared. The optical coupling layer 111 can be made of single crystal silicon, for example.
［実施の形態２］
　次に、本発明の実施の形態２に係る半導体レーザについて図７Ａ、図７Ｂを参照して説明する。この半導体レーザは、基板１０１の上に、導波方向に延在するコア形状に形成された活性層１０３を備え、共振器内に回折格子１１２を備えるＤＦＢレーザである。 [Embodiment 2]
Next, a semiconductor laser according to Embodiment 2 of the present invention will be described with reference to FIGS. 7A and 7B. This semiconductor laser is a DFB laser having an active layer 103 formed in a core shape extending in the waveguide direction on a substrate 101 and having a diffraction grating 112 in the resonator.
　この半導体レーザは、まず、基板１０１の上に第１クラッド層１０２が形成され、第１クラッド層１０２の上に、活性層１０３を備える。基板１０１は、例えば、Ｓｉから構成され、第１クラッド層１０２は、例えば、酸化シリコンから構成されている。また、活性層１０３を挾んで活性層１０３に接して形成されたｐ型半導体層１０４およびｎ型半導体層１０５を備える。また、活性層１０３の上に形成された第２クラッド層１０６と、ｐ型半導体層１０４およびｎ型半導体層１０５に接続するｐ電極１０７およびｎ電極１０８とを備える。 This semiconductor laser first has a first clad layer 102 formed on a substrate 101 and an active layer 103 on the first clad layer 102 . The substrate 101 is made of Si, for example, and the first clad layer 102 is made of silicon oxide, for example. It also has a p-type semiconductor layer 104 and an n-type semiconductor layer 105 formed in contact with the active layer 103 with the active layer 103 interposed therebetween. It also includes a second clad layer 106 formed on the active layer 103 , and a p-electrode 107 and an n-electrode 108 connected to the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
　この例では、ｐ型半導体層１０４およびｎ型半導体層１０５は、例えば、ＩｎＰからなる半導体層１０９に不純物を導入することで形成されている。また、ｐ型半導体層１０４とｎ型半導体層１０５との間において、活性層１０３は、半導体層１０９に埋め込まれて形成されている。また、活性層１０３と光結合可能な状態で第１クラッド層１０２に埋め込まれて、活性層１０３に沿って延在するコア形状に形成された光結合層１１３を備える。光結合層１１３は、例えば、単結晶シリコンから構成することができる。 In this example, the p-type semiconductor layer 104 and the n-type semiconductor layer 105 are formed by introducing impurities into the semiconductor layer 109 made of InP, for example. Also, the active layer 103 is embedded in the semiconductor layer 109 between the p-type semiconductor layer 104 and the n-type semiconductor layer 105 . Further, an optical coupling layer 113 formed in a core shape extending along the active layer 103 is embedded in the first clad layer 102 so as to be optically coupled with the active layer 103 . The optical coupling layer 113 can be made of single crystal silicon, for example.
　上述した構成に加え、実施の形態に係る半導体レーザは、図７Ｂに示すように、共振器内に、ストップバンドが変調された第１領域１２１および第２領域１２２を備える。第１領域１２１と第２領域１２２とは、導波方向に間隔を開けて配置されている。第１領域１２１および第２領域１２２は、光結合層１１３の幅を変えることで、ストップバンドを変調させている。 In addition to the configuration described above, the semiconductor laser according to the embodiment includes a first region 121 and a second region 122 whose stopbands are modulated in the resonator, as shown in FIG. 7B. The first region 121 and the second region 122 are spaced apart in the waveguide direction. The first region 121 and the second region 122 modulate the stopband by changing the width of the optical coupling layer 113 .
　第１領域１２１および第２領域１２２は、導波方向の光結合層１１３の幅が他の領域とは異なるものとされている。また、第１領域１２１の光結合層１１３の幅は、他の領域より大きくされ、第２領域１２２の光結合層１１３の幅は、他の領域より小さくされている。なお、図７Ｂは、光結合層１１３の構成を示す平面図であり、図７Ｂの紙面右から左の方向が、導波方向となっている。 The first region 121 and the second region 122 are different from other regions in the width of the optical coupling layer 113 in the waveguide direction. Also, the width of the optical coupling layer 113 in the first region 121 is made larger than that in other regions, and the width of the optical coupling layer 113 in the second region 122 is made smaller than that in other regions. Note that FIG. 7B is a plan view showing the configuration of the optical coupling layer 113, and the direction from the right to the left on the paper surface of FIG. 7B is the waveguide direction.
　また、この例では、共振器内の両端に、ストップバンドが変調された第３領域１２３および第４領域１２４を備える。第３領域１２３および第４領域１２４も、光結合層１１３の幅を変えることで、ストップバンドを変調させている。共振器内の一端側の第３領域１２３および他端側の第４領域１２４の導波方向の光結合層１１３の幅は、第３領域１２３および第４領域１２４より内側の領域の幅より大きくされている。 Also, in this example, a third region 123 and a fourth region 124 whose stopbands are modulated are provided at both ends of the resonator. The third region 123 and fourth region 124 also modulate the stopband by changing the width of the optical coupling layer 113 . The width of the optical coupling layer 113 in the waveguide direction of the third region 123 on one end side and the fourth region 124 on the other end side in the resonator is larger than the width of the region inside the third region 123 and the fourth region 124 . It is
　上述したように、光結合層１１３を設け、さらに、光結合層１１３の幅を、第１領域１２１、第２領域１２２、第３領域１２３、第４領域１２４において変化させることで、図３に示すように、共振器におけるストップバンド波長が変調される。光結合層１１３の幅を変化させることで、回折格子１１２の結合係数や活性層１０３における光閉じ込めの割合を変化させることができ、上述したように、共振器におけるストップバンド波長を変調させることができる。 As described above, by providing the optical coupling layer 113 and changing the width of the optical coupling layer 113 in the first region 121, the second region 122, the third region 123, and the fourth region 124, the optical coupling layer 113 shown in FIG. As shown, the stopband wavelength in the cavity is modulated. By changing the width of the optical coupling layer 113, the coupling coefficient of the diffraction grating 112 and the rate of optical confinement in the active layer 103 can be changed, and as described above, the stopband wavelength in the resonator can be modulated. can.
　このように、実施の形態２においても、共振器におけるストップバンド波長を変調させることができるので、前述した実施の形態１と同様に、ＤＦＢレーザとは別に外部共振器を用いることなく、ＰＰＲを発現することができる。このため、ＤＦＢレーザからの出射光とフィードバック光の位相を合わせる必要がなくなる。この結果、実施の形態２においても、ＤＦＢレーザの特定の電流注入条件でなくともＰＰＲが発現するため、動作環境によらず高速な直接変調が実現する。また、実施の形態２においても、例えばヒータなどの位相調整機構を必要としないため、低消費電力化に対して有効である。 Thus, in the second embodiment as well, the stop band wavelength in the resonator can be modulated. can be expressed. Therefore, it is not necessary to match the phases of the light emitted from the DFB laser and the feedback light. As a result, in the second embodiment as well, the PPR is generated even if the current injection conditions are not specific for the DFB laser, so high-speed direct modulation is realized regardless of the operating environment. Moreover, since the second embodiment does not require a phase adjustment mechanism such as a heater, it is effective in reducing power consumption.
［実施の形態３］
　次に、本発明の実施の形態３に係る半導体レーザについて図８Ａ、図８Ｂ、図８Ｃを参照して説明する。この半導体レーザは、基板１０１の上に、導波方向に延在するコア形状に形成された活性層１０３を備え、共振器内に回折格子１１４を備えるＤＦＢレーザである。 [Embodiment 3]
Next, a semiconductor laser according to Embodiment 3 of the present invention will be described with reference to FIGS. 8A, 8B, and 8C. This semiconductor laser is a DFB laser having an active layer 103 formed in a core shape extending in the waveguide direction on a substrate 101 and having a diffraction grating 114 in the resonator.
　この半導体レーザは、まず、基板１０１の上に第１クラッド層１０２が形成され、第１クラッド層１０２の上に、活性層１０３を備える。基板１０１は、例えば、Ｓｉから構成され、第１クラッド層１０２は、例えば、酸化シリコンから構成されている。また、活性層１０３を挾んで活性層１０３に接して形成されたｐ型半導体層１０４およびｎ型半導体層１０５を備える。また、活性層１０３の上に形成された第２クラッド層１０６と、ｐ型半導体層１０４およびｎ型半導体層１０５に接続するｐ電極１０７およびｎ電極１０８とを備える。 This semiconductor laser first has a first clad layer 102 formed on a substrate 101 and an active layer 103 on the first clad layer 102 . The substrate 101 is made of Si, for example, and the first clad layer 102 is made of silicon oxide, for example. It also has a p-type semiconductor layer 104 and an n-type semiconductor layer 105 formed in contact with the active layer 103 with the active layer 103 interposed therebetween. It also includes a second clad layer 106 formed on the active layer 103 , and a p-electrode 107 and an n-electrode 108 connected to the p-type semiconductor layer 104 and the n-type semiconductor layer 105 .
　この例では、ｐ型半導体層１０４およびｎ型半導体層１０５は、例えば、ＩｎＰからなる半導体層１０９に不純物を導入することで形成されている。また、ｐ型半導体層１０４とｎ型半導体層１０５との間において、活性層１０３は、半導体層１０９に埋め込まれて形成されている。また、活性層１０３と光結合可能な状態で第１クラッド層１０２に埋め込まれて、活性層１０３に沿って延在するコア形状に形成された光結合層１１３を備える。光結合層１１３は、例えば、単結晶シリコンから構成することができる。 In this example, the p-type semiconductor layer 104 and the n-type semiconductor layer 105 are formed by introducing impurities into the semiconductor layer 109 made of InP, for example. Also, the active layer 103 is embedded in the semiconductor layer 109 between the p-type semiconductor layer 104 and the n-type semiconductor layer 105 . Further, an optical coupling layer 113 formed in a core shape extending along the active layer 103 is embedded in the first clad layer 102 so as to be optically coupled with the active layer 103 . The optical coupling layer 113 can be made of single crystal silicon, for example.
　上述した構成に加え、実施の形態に係る半導体レーザは、図８Ｂに示すように、共振器内に、ストップバンドが変調された第１領域１２１および第２領域１２２を備える。第１領域１２１と第２領域１２２とは、導波方向に間隔を開けて配置されている。第１領域１２１および第２領域１２２は、光結合層１１３の幅を変えることで、ストップバンドを変調させている。 In addition to the configuration described above, the semiconductor laser according to the embodiment includes, as shown in FIG. 8B, a first region 121 and a second region 122 whose stopbands are modulated in the resonator. The first region 121 and the second region 122 are spaced apart in the waveguide direction. The first region 121 and the second region 122 modulate the stopband by changing the width of the optical coupling layer 113 .
　第１領域１２１および第２領域１２２は、導波方向の光結合層１１３の幅が他の領域とは異なるものとされている。また、第１領域１２１の光結合層１１３の幅は、他の領域より大きくされ、第２領域１２２の光結合層１１３の幅は、他の領域より小さくされている。なお、図８Ｂは、光結合層１１３の構成を示す平面図であり、図８Ｂの紙面右から左の方向が、導波方向となっている。 The first region 121 and the second region 122 are different from other regions in the width of the optical coupling layer 113 in the waveguide direction. Also, the width of the optical coupling layer 113 in the first region 121 is made larger than that in other regions, and the width of the optical coupling layer 113 in the second region 122 is made smaller than that in other regions. Note that FIG. 8B is a plan view showing the configuration of the optical coupling layer 113, and the direction from the right to the left on the paper surface of FIG. 8B is the waveguide direction.
　また、実施の形態３では、図８Ｃに示すように、共振器内の両端に、ストップバンドが変調された第３領域１２３および第４領域１２４を備える。第３領域１２３および第４領域１２４は、回折格子１１４のデューティー比を変えることで、ストップバンドを変調させている。共振器内の一端側の第３領域１２３および他端側の第４領域１２４の導波方向の回折格子１１４のデューティー比は、第３領域１２３および第４領域１２４より内側の領域のデューティー比より小さくされている。 In addition, in Embodiment 3, as shown in FIG. 8C, the third region 123 and the fourth region 124 whose stopbands are modulated are provided at both ends in the resonator. The third region 123 and fourth region 124 modulate the stop band by changing the duty ratio of the diffraction grating 114 . The duty ratio of the diffraction grating 114 in the waveguide direction of the third region 123 on one end side and the fourth region 124 on the other end side in the resonator is higher than the duty ratio of the region inside the third region 123 and the fourth region 124. made smaller.
　上述したように、第１領域１２１、第２領域１２２、第３領域１２３、第４領域１２４を設けることで、図３に示すように、共振器における第１領域１２１、第２領域１２２、第３領域１２３、第４領域１２４のストップバンド波長が変調される。 As described above, by providing the first region 121, the second region 122, the third region 123, and the fourth region 124, as shown in FIG. The stop band wavelengths of the 3rd region 123 and the 4th region 124 are modulated.
　このように、実施の形態３においても、共振器におけるストップバンド波長を変調させることができるので、前述した実施の形態１と同様に、ＤＦＢレーザとは別に外部共振器を用いることなく、ＰＰＲを発現することができる。このため、ＤＦＢレーザからの出射光とフィードバック光の位相を合わせる必要がなくなる。この結果、実施の形態３においても、ＤＦＢレーザの特定の電流注入条件でなくともＰＰＲが発現するため、動作環境によらず高速な直接変調が実現する。また、実施の形態３においても、例えばヒータなどの位相調整機構を必要としないため、低消費電力化に対して有効である。 Thus, in the third embodiment as well, the stop band wavelength in the resonator can be modulated. can be expressed. Therefore, it is not necessary to match the phases of the light emitted from the DFB laser and the feedback light. As a result, in the third embodiment as well, the PPR is generated without the specific current injection conditions of the DFB laser, so high-speed direct modulation is realized regardless of the operating environment. Moreover, since the third embodiment does not require a phase adjustment mechanism such as a heater, it is effective in reducing power consumption.
　以上に説明したように、本発明によれば、回折格子のピッチを変えるなどにより、共振器内にストップバンドが変調された第１領域および第２領域を備えるようにしたので、分布帰還型レーザなどにおいて、光子－光子共鳴が容易に利用できるようになる。 As described above, according to the present invention, the first region and the second region in which the stop band is modulated are provided in the resonator by changing the pitch of the diffraction grating. etc., making photon-photon resonance readily available.
　なお、本発明は以上に説明した実施の形態に限定されるものではなく、本発明の技術的思想内で、当分野において通常の知識を有する者により、多くの変形および組み合わせが実施可能であることは明白である。 It should be noted that the present invention is not limited to the embodiments described above, and many modifications and combinations can be implemented by those skilled in the art within the technical concept of the present invention. It is clear.
　１０１…基板、１０２…第１クラッド層、１０３…活性層、１０４…ｐ型半導体層、１０５…ｎ型半導体層、１０６…第２クラッド層、１０７…ｐ電極、１０８…ｎ電極、１０９…半導体層、１１０…回折格子。 DESCRIPTION OF SYMBOLS 101... Substrate 102... First clad layer 103... Active layer 104... P-type semiconductor layer 105... N-type semiconductor layer 106... Second clad layer 107... P-electrode 108... N-electrode 109... Semiconductor Layer, 110... Grating.

Claims (6)

  1. 　基板の上に形成された第１クラッド層と、
    　前記第１クラッド層の上に、導波方向に延在するコア形状に形成された活性層と、
    　前記活性層を挾んで前記活性層に接して形成されたｐ型半導体層およびｎ型半導体層と、
    　前記活性層の上に形成された第２クラッド層と、
    　前記ｐ型半導体層および前記ｎ型半導体層に接続するｐ電極およびｎ電極と
    　を備え、
    　共振器内に回折格子を備える半導体レーザであって、
    　前記共振器内に、導波方向の前記回折格子のピッチが他の領域とは異なる第１領域および第２領域を備え、
    　前記第１領域と前記第２領域とは、導波方向に間隔を開けて配置され、
    　前記第１領域の前記回折格子のピッチは、前記他の領域より大きくされ、
    　前記第２領域の前記回折格子のピッチは、前記他の領域より小さくされている
    　ことを特徴とする半導体レーザ。     a first cladding layer formed on a substrate;
    an active layer formed in a core shape extending in a waveguide direction on the first cladding layer;
    a p-type semiconductor layer and an n-type semiconductor layer formed in contact with the active layer with the active layer interposed therebetween;
    a second clad layer formed on the active layer;
    A p-electrode and an n-electrode connected to the p-type semiconductor layer and the n-type semiconductor layer,
    A semiconductor laser comprising a diffraction grating in a cavity,
    The resonator includes a first region and a second region in which the pitch of the diffraction grating in the waveguide direction is different from other regions,
    the first region and the second region are spaced apart in a waveguide direction,
    the pitch of the diffraction grating in the first region is made larger than that in the other regions;
    A semiconductor laser, wherein the pitch of the diffraction grating in the second region is smaller than that in the other regions.
  2. 　請求項１記載の半導体レーザにおいて、
    　前記第１領域の前記回折格子のピッチは、前記第２領域の前記回折格子のピッチの２倍とされていることを特徴とする半導体レーザ。     2. The semiconductor laser of claim 1, wherein
    A semiconductor laser according to claim 1, wherein the pitch of said diffraction grating in said first region is twice the pitch of said diffraction grating in said second region.
  3. 　請求項１または２記載の半導体レーザにおいて、
    　前記共振器内の一端側の第３領域および他端側の第４領域の導波方向の前記回折格子のデューティー比は、前記第３領域および前記第４領域より内側の領域のデューティー比より小さくされている
    　ことを特徴とする半導体レーザ。     3. The semiconductor laser according to claim 1, wherein
    The duty ratio of the diffraction grating in the waveguide direction of the third region on one end side and the fourth region on the other end side in the resonator is smaller than the duty ratio of the region inside the third region and the fourth region. A semiconductor laser characterized by:
  4. 　基板の上に形成された第１クラッド層と、
    　前記第１クラッド層の上に、導波方向に延在するコア形状に形成された活性層と、
    　前記活性層を挾んで前記活性層に接して形成されたｐ型半導体層およびｎ型半導体層と、
    　前記活性層の上に形成された第２クラッド層と、
    　前記ｐ型半導体層および前記ｎ型半導体層に接続するｐ電極およびｎ電極と、
    　前記活性層と光結合可能な状態で前記第１クラッド層または前記第２クラッド層に埋め込まれて、前記活性層に沿って延在するコア形状に形成された光結合層と
    　を備え、
    　共振器内に回折格子を備える半導体レーザであって、
    　前記共振器内に、導波方向に垂直な方向の前記光結合層の幅が他の領域とは異なる第１領域および第２領域を備え、
    　前記第１領域と前記第２領域とは、導波方向に間隔を開けて配置され、
    　前記第１領域の前記光結合層の幅は、前記他の領域より大きくされ、
    　前記第２領域の前記光結合層の幅は、前記他の領域より小さくされている
    　ことを特徴とする半導体レーザ。     a first cladding layer formed on a substrate;
    an active layer formed in a core shape extending in a waveguide direction on the first cladding layer;
    a p-type semiconductor layer and an n-type semiconductor layer formed in contact with the active layer with the active layer interposed therebetween;
    a second clad layer formed on the active layer;
    a p-electrode and an n-electrode connected to the p-type semiconductor layer and the n-type semiconductor layer;
    an optical coupling layer formed in a core shape extending along the active layer and embedded in the first clad layer or the second clad layer so as to be optically coupled with the active layer;
    A semiconductor laser comprising a diffraction grating in a cavity,
    The resonator includes a first region and a second region, the width of the optical coupling layer in the direction perpendicular to the waveguide direction being different from other regions,
    the first region and the second region are spaced apart in a waveguide direction,
    The width of the optical coupling layer in the first region is made larger than that in the other regions,
    A semiconductor laser, wherein the width of the optical coupling layer in the second region is smaller than that in the other region.
  5. 　請求項４記載の半導体レーザにおいて、
    　前記共振器内の一端側の第３領域および他端側の第４領域の前記光結合層の幅は、前記他の領域より大きくされている
    　ことを特徴とする半導体レーザ。     5. The semiconductor laser according to claim 4,
    A semiconductor laser according to claim 1, wherein widths of the optical coupling layer in a third region on one end side and a fourth region on the other end side in the resonator are larger than those of the other regions.
  6. 　請求項４記載の半導体レーザにおいて、
    　前記共振器内の一端側の第３領域および他端側の第４領域の導波方向の前記回折格子のデューティー比は、前記第３領域および前記第４領域より内側の領域のデューティー比より小さくされている
    　ことを特徴とする半導体レーザ。     5. The semiconductor laser according to claim 4,
    The duty ratio of the diffraction grating in the waveguide direction of the third region on one end side and the fourth region on the other end side in the resonator is smaller than the duty ratio of the region inside the third region and the fourth region. A semiconductor laser characterized by:
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